1. Field of the Invention
The present invention is in the field of medical apparatus and more specifically relates to an improvement in a hypodermic syringe to permit the user of the syringe to determine readily whether the syringe has been tampered with.
2. The Prior Art
In a hypodermic syringe cartridge of the type known in the prior art, a rubber drive piston is mounted within a tubular glass member that serves as a container for an injectable fluid. The drive piston includes a front face that is in contact with the fluid in the cartridge. Typically, a small screw is embedded in the rubber drive piston and extends through the rear face of the drive piston. The purpose of this screw is to permit an actuator rod to be connected to the drive piston. The injectable fluid is expelled from the syringe when the user pushes on the actuator rod thereby causing the drive piston to advance against the fluid.
There have been instances where persons have removed narcotics from such a syringe without authorization, and have then replaced the pilfered fluid with a substitute fluid. In order to accomplish this, it is necessary for the drive piston to be advanced against the fluid so as to express some of the fluid into another container and thereafter, the tip of the hypodermic needle is inserted into a substitute fluid which is then aspirated into the hypodermic syringe cartridge by retracting the drive piston in the direction opposite to the direction in which it was originally advanced. After this sequence has been carried out on a cartridge of the type used in the prior art, it is practically impossible to detect that the cartridge has been tampered with. The present invention is an improvement to a hypodermic syringe cartridge which will alert a later user of the cartridge to the fact that the cartridged has previously been tampered with.